This invention is related to abrasive articles, particularly abrasive articles especially suited for use in critical or controlled environments.
An ever increasing number of industrial operations require isolation from potential ubiquitous physical and chemical contaminants. Conversely, other industrial operations may require quarantine from the general environment due to their toxic or infectious nature. Such needs are generally met by the design, fabrication, and use of so-called xe2x80x9cclean roomsxe2x80x9d (also known as xe2x80x9cwhite roomsxe2x80x9d).
Such facilities have found widespread use in the manufacture of semiconductor devices, where the presence of external contaminants such as unwanted particles and ions must be minimized. Operations such as, for example, crystal growth, ion implantation, metal deposition, and etching are typically carried out in low pressure (vacuum) chambers or reactors that are operated in clean room environments. Following use for a time, these chambers inevitably become soiled and therefore require cleaning. Depending on the nature of the contamination, abrasive articles may be required to remove tenaciously-held contaminants. Such abrasive operations by definition generate particulate materials that may contaminate the clean room environment. Further, the abrasive articles themselves may convey unwanted particles and/or ionic moieties into the chamber and/or clean room. There thus is a need for an abrasive article for use in critical, clean room environments. Such an abrasive article should efficaciously remove residue from reactor surfaces, minimize the release of particles into the clean room environment, and minimize transfer of ionic contaminants to the reactor and/or the clean room.
One embodiment of this present invention provides a flexible abrasive article comprising a foraminous substrate, at least one binder, and abrasive particles, wherein the abrasive article contains minimal amount of releaseable physical and chemical contaminants and when used to clean a surface provides a clean workpiece with minimal amounts of physical and chemical contaminants and does not damage the workpiece surface.
Another embodiment of this invention provides a method of making a flexible abrasive article comprising the steps of:
Providing a foraminous substrate;
Coating the foraminous substrate with a make coating;
Coating the coated substrate with abrasive granules;
Curing the granule coated substrate;
Coating the granule coated cured substrate with a size coating;
Curing the size-coated substrate;
Converting the cured, size-coated substrate into useful shaped abrasive article;
Post-cleaning the abrasive articles to remove potential workpiece contaminants; and
Packaging the post-cleaned abrasive articles.
xe2x80x9cFlexible abrasive articlexe2x80x9d refers to an abrasive article, which when folded onto itself with the abrasive surface exposed, that does result in knife-edging of the abrasive coating.
xe2x80x9cForaminous substratexe2x80x9d refers to a porous, organic substrate having openings defined by interconnecting voids throughout at least one surface of the substrate. For example, either an open-celled foam substrate or lofty, fibrous, nonwoven web or fabric qualifies as a foraminous substrate.
xe2x80x9cMake coat precursorxe2x80x9d refers to the coatable resinous adhesive material applied to the coatable surfaces of the openings of the foraminous substrate to secure abrasive particles thereto.
xe2x80x9cMake coatxe2x80x9d refers to the layer of cured resin over the coatable surfaces of the openings of the foraminous substrate formed by hardening the make coat precursor.
xe2x80x9cSize coat precursorxe2x80x9d refers to the coatable resinous adhesive material applied to the coatable surfaces of the openings of the foraminous substrate over the make coat.
xe2x80x9cSize coatxe2x80x9d refers to the layer of cured resin over the coatable surfaces of the openings of the foraminous substrate formed by hardening the size coat precursor.
xe2x80x9cCuredxe2x80x9d or xe2x80x9cfully curedxe2x80x9d means a hardened polymerized curable coatable resin.
xe2x80x9cFine abrasive particlesxe2x80x9d refers to abrasively effective particles comprising any of the materials set forth herein and having distribution of particle sizes wherein a highly preferred median particle diameter is about 60 microns or less. A spherical particle shape is assumed in referring to the median particle diameter, based on standard test methods available for the determination of particle diameters such as, for example, ANSI test method B74.18-1884.
xe2x80x9cSubstantially uniformxe2x80x9d refers to the distribution of fine abrasive particles in the finished articles that are distributed along coatable surfaces of the contours and walls i.e., coatable surfaces, defined by interstices or voids without significant agglomeration of the resin and the particles, as may be visually observed by microscopic examination of the surfaces. In the finished article, the majority of the particles are positioned along the coatable surfaces of the openings to be abrasively effective in the initial application of the article.
The abrasive articles of this invention may be provided in the form of hand pads, endless belts, discs, densified or compressed wheels and the like. Additionally, the articles of the invention may be laminated to other articles such as nonwoven, closed cell foam, open cell foam, or rigid foam substrates and the like or the articles may be provided a in a roll form with or without perforations therein.
In the preparation of the foregoing articles, a foraminous substrate is prepared or is otherwise provided. A make coat precursor composition is applied to a surface of the foraminous substrate to form a first coating layer. A plurality of fine abrasive particles are applied to the first coating layer, and the make coat precursor composition is at least partially cured. Optionally, a size coat precursor composition is applied over the abrasive particles and the first coating layer to form a second coating layer. The first and second coating layers are cured to affix the abrasive particles to the coatable surfaces of the openings of the foraminous substrate to provide the abrasive article wherein the particles are affixed to the surfaces in a substantially uniform distribution along their contours.
The fine abrasive particles are deposited onto the make coat precursor, preferably by depositing the particles first on one major surface of the foraminous substrate and then over the second major surface of the foraminous substrate using the deposition method described in U.S. Pat. No. 5,863,305, incorporated by reference herein. Larger abrasive particles, i.e., greater than 60 micron diameter, are preferably applied to the make coat precursor by known methods such as drop coating or electrostatic coating. Preferably, the make and size coat precursors are thermosetting, coatable, polyurethane resins. Likewise, the optional size coat, when applied to the article, is preferably applied over the at least partially cured make coat. The make coat precursor and size coat precursor are then fully cured to provide the flexible abrasive articles of the invention, and the thus prepared articles may be further processed to provide hand pads, endless belts, discs, densified or compressed wheels and the like.